Add more push and workflow_dispatch triggers

- Trigger `msrv.yml` on the push event, for the same branches
  for which `ci.yml` is triggered on it. That is, make the
  corresponding change to the MSRV workflow that was made to the
  test workflow.

- Remove outdated comments on `msrv.yml`. These comments already
  disagreed with the code, since they named `master` when the
  branch was `main`, and suggested that all pull requests would
  trigger the workflow when really was (and continues to be) also
  limited by branch.

- Add `workflow_dispatch` to the `ci.yml` and `msrv.tml` workflows,
  so they can be manually run even for branches that are not named,
  and in the case of `ci.yml`, so it can be manually run even when
  changes are not made to any of the paths that are also needed
  to trigger it on the push or pull_request events.

- Put `workflow_dispatch` last in the `release.yml` workflow that
  already had it. Currently it is a secondary way to trigger all
  workflows that include it. It was in practice the primary way to
  trigger `release.yml` when the push trigger was broken, but that
  is no longer the case since 286e388 (Byron#1475). Even in testing, it
  is now most often run by pushing a tag. This brings its style in
  line with the style in `cron.yml`, where `workflow_dispatch` was
  already a secondary way to trigger the workflow and listed second.

.github/workflows/ci.yml

@@ -35,6 +35,7 @@ on:
  - 'gix*/**'
  - '*.toml'
  - Makefile
+ workflow_dispatch:
 
 jobs:
  pure-rust-build:

.github/workflows/msrv.yml

@@ -1,13 +1,17 @@
 name: Minimum Supported Rust Version
 
 on:
- # Trigger the workflow on push to master or any pull request
- # Ignore all tags
  push:
- branches: [ main ]
- tags-ignore: [ '*' ]
+ branches:
+ - main
+ - 'run-ci/**'
+ - '**/run-ci/**'
+ tags-ignore:
+ - '*'
  pull_request:
- branches: [ main ]
+ branches:
+ - main
+ workflow_dispatch:
 
 jobs:
  rustfmt:

.github/workflows/release.yml

@@ -4,13 +4,13 @@
 name: release
 
 on:
- workflow_dispatch:
  push:
  # Enable when testing release infrastructure on a branch.
  # branches:
  # - fix-releases
  tags:
  - 'v*'
+ workflow_dispatch:
 
 defaults:
  run: